Overview

Gestational diabetes is one of the most common conditions during pregnancy. In the United States, it is standard to test all pregnant women for gestational diabetes, even if they do not have any risk factors. During pregnancy, your body naturally becomes more resistant to insulin. That means you absorb less glucose and more remains in your blood. You can imagine that a growing baby needs a lot of energy, so this adaptation makes sense and allows more glucose to reach your baby. For most moms, this works just like it is supposed to. Your pancreas reacts to higher blood glucose by producing more insulin. For some expecting mothers, their pancreas can’t keep up with the increased demand for additional insulin, and more glucose builds up in their blood. This article breaks down gestational diabetes, testing, treatment, risks, and how this affects your pregnancy, birth, and baby. 

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Glucose Metabolism

Your body breaks down foods into glucose, a type of sugar. Glucose is used throughout your body for energy. To help muscles, fat, and other cells absorb glucose for fuel, your pancreas produces a hormone called insulin.

There are different classifications for people who do not have normal insulin production and have abnormally high blood glucose. Prediabetic means that your blood sugar levels are high, and you are at a higher risk of developing type II diabetes later in life. Type I diabetes means that your body does not produce insulin, and people who are Type I diabetic are often born with this condition. Type II diabetes is when people do not respond as well to insulin and may not produce enough insulin. This is usually something that people develop later in life, not a condition from birth.

Glucose Metabolism During Pregnancy

When you are pregnant, your body naturally becomes more resistant to insulin. That means you absorb less glucose and more remains in your blood. You can imagine that a growing baby needs a lot of energy, so this adaptation makes sense and allows more glucose to reach your baby. For most moms, this works just like it is supposed to. Your pancreas reacts to higher blood glucose by producing more insulin to keep your blood sugar levels in check. 

For some expecting mothers, their pancreas can’t keep up with the high demand for additional insulin, and more glucose builds up in their blood. This is known as hyperglycemia. Insulin doesn’t cross the placenta, but glucose does. The extra glucose that is more than your baby needs is stored as fat.  

Gestational Diabetes

Gestational Diabetes is a type of diabetes that occurs during your pregnancy and goes away after the birth of your baby. There is a lot of evidence that gestational diabetes does increase your risk for adverse pregnancy outcomes.

As your baby’s body is trying to deal with the high levels of glucose, its pancreas responds by producing more insulin. This can result in them having lower blood glucose levels at birth, which can be associated with breathing problems. Babies born with excess insulin are at a higher risk for obesity and Type 2 diabetes. A baby born to a mother with gestational diabetes is also at a higher risk for jaundice, stillbirth, preterm labor, and NICU (neonatal intensive care unit) admission. A risk of your baby gaining additional weight is macrosomia, defined as a baby who weighs more than 4,500 g (9 lb, 15 oz). This can increase the risk of injury to their shoulder during birth, known as shoulder dystocia, or other birth injuries. 

If you have gestational diabetes, you have a higher risk of hypertension, preeclampsia, and cesarean birth. You are also more likely to get gestational diabetes in a subsequent pregnancy and develop type 2 diabetes later in life.  

Prevalence of Gestational Diabetes

According to the CDC, gestational diabetes affects 2-10% of pregnancies in the United States. Some research has pinpointed a rate of 6%. Rates of gestational diabetes vary widely based on race, age, and weight. Research shows that the rates differ significantly among ethnicities. In Black women, it is 4.8%, White 5.3%, Hispanic 6.6%, Native Hawaiian/Pacific Islander 8.4%, American Indian/Alaska Native 9.2%, Asian 11.1%. Rates of gestational diabetes increase with age. Under 20 is 1.9%, 20-24 3.3%, 25-29 5.1%, 30-34 7%, 35-39 9.6%, and expecting mothers over 40 12.8%. Rates also vary by weight. In underweight women, it is 2.9%, increasing to 13.6% in obese women.

Keeping these statistics in mind, some other factors can increase your risk of developing gestational diabetes. If you have a family history of diabetes, you are at a higher risk. Your risk increases if you had gestational diabetes in a previous pregnancy or abnormal glucose metabolism in the past. 

Gestational Diabetes Testing

In the United States, it is standard procedure to test all pregnant women for gestational diabetes, even if they do not have any risk factors. Testing for gestational diabetes starts with a screening test and, depending on the results, may indicate the need for a second diagnostic test.

Glucose Challenge Screening

The glucose challenge screening is a preliminary screening test to evaluate how your body processes sugar. This screening test is a standard routine test between 24-28 weeks. If you are considered high-risk, you will likely test early in your pregnancy. If someone high-risk tests negative early on, they may test again in the third trimester. Some practitioners argue that women at low risk for gestational diabetes should not be required to be routinely tested, although that would mean around 4% of cases could go undiagnosed.

During the glucose challenge screening test, your blood is drawn to get a baseline reading, and then you are asked to drink a sweet glucose liquid within five minutes and then have blood drawn one hour later. A high glucose level in your blood may indicate that your body is not processing sugar effectively.

The “normal” blood sugar level threshold is 130 or 140 milligrams per deciliter or lower, which may vary between providers. Like any screening test isn’t perfect, and the sensitivity of this test is 74%. A positive result correctly identifies 74% of women with gestational diabetes. It has a specificity of 77%, which means 33% of women without gestational diabetes will get a positive result. If the results of this screen are positive, you may take the glucose tolerance test to diagnose whether you do have gestational diabetes.

Some alternatives to the glucose challenge screening include eating jelly beans instead of drinking the glucose drink or blood monitoring at home. If you want to explore some different options for gestational diabetes testing, see this episode.

Glucose Tolerance Test

The glucose challenge screening indicates your likelihood of gestational diabetes. If you have a high level of glucose on the screening test, you will go on to take the glucose tolerance test, which can rule out or diagnose the condition. Before taking the glucose tolerance test, your doctor will ask you to make sure and eat at least 150mg of carbohydrates for three days. 150 mg of carbs is what you will get from a slice or two of bread. You should not eat or drink anything but sips of water for 14 hours before the test. For this reason, it is best to schedule the test for first thing in the morning. A technician will draw blood to measure your baseline fasting blood glucose level. You will drink a glucose solution (75g or 100g), and your blood will be drawn and tested every hour for the next three hours.

This test is more accurate than the screening test. If only one of your readings returns abnormal, your doctor may suggest changes to your diet and test you again later in the pregnancy. If two or more of your readings come back abnormal, you will be diagnosed with gestational diabetes, and your doctor or midwife will talk to you about a treatment plan. About one-third of women who exceed the limit on the screening test are diagnosed with gestational diabetes on the second test. See this episode for more information on testing for gestational diabetes. 

Gestational Diabetes Treatment Options

If you are diagnosed with gestational diabetes, your doctor or midwife will require you to monitor your blood glucose levels. You will need to keep a log of the testing results from using a blood glucose meter. This requires you to prick your finger and put a drop of blood on a test strip in a meter that can detect the glucose level. There are continuous glucose monitors that you wear, although they are much more expensive, and the use of those has not been widely adopted.

The frequency of when you will need to monitor your blood glucose will depend on the particulars of your results and how you are managing blood sugar levels. According to ACOG, there is insufficient evidence to define the optimal frequency of blood glucose testing. The general recommendation is four times per day, once after fasting and again after each meal. Along with monitoring, treatment starts with modification of your diet and exercise habits and can progress to medications. 

Lifestyle Modifications

The first line of therapy for managing glucose is lifestyle modification, including diet and exercise. While these require work on your end, there is no downside to improving your diet and activity levels and a host of short and long-term benefits. A Cochrane review found that lifestyle interventions benefited women with gestational diabetes and their babies.

Diet

Dietary modification, sometimes called medical nutrition therapy, is the first step in managing gestational diabetes. The general recommendation is to limit your carbohydrate intake to 33-40% of your total calorie intake, choose complex over simple carbohydrates, and spread your food intake over three meals and two snacks daily. Your doctor or midwife should discuss nutrition and diet in-depth with you. You may also speak with a dietitian to assist you. Keeping a food journal or logging your meals in an app can be very helpful in monitoring your diet.

Exercise 

In addition to diet, your care provider will recommend exercise to lower your blood glucose levels. When your liver releases additional glucose to fuel your workout, your pancreas produces more insulin. Research shows that exercise results in lower instances of gestational diabetes and abnormal glucose tolerance.

ACOG recommends that women with gestational diabetes aim for 30 minutes of moderate-intensity aerobic exercise at least five days a week or at least 150 minutes per week. They also note that simple exercise, such as walking for 10–15 minutes after each meal, can lead to improved glycemic control. Regular exercise during pregnancy also decreases your risk of other complications, including preeclampsia and cesarean birth. In addition to promoting healthy weight gain, working out can ease common pregnancy symptoms like constipation and back pain. See this episode for an overview of exercise in pregnancy, including recommendations and what activities you should avoid. Nearly every form of exercise can be modified to be safe during pregnancy, and there are separate episodes on yoga, cardio, and strength training.

Medication 

If diet and exercise are not working effectively to regulate your blood glucose levels, your doctor or midwife may suggest medication. The available treatment options for medication are insulin or oral antidiabetics. 

Insulin 

Insulin effectively lowers your blood glucose levels by helping you absorb glucose better and use it for fuel. If you are not producing enough insulin on your own, you administer insulin with an injection. There is quite a bit of data on many types of insulin available, and several are considered safe during pregnancy. Insulin does not cross the placenta. They can vary significantly in how quickly they work and how long they last. The Type and dose of insulin will largely depend on your care provider.

Oral Medications 

There are two options for oral medications to treat gestational diabetes. The antidiabetic medicines are glyburide and metformin. These are less expensive than insulin, do not require an injection, and are taken orally. Unlike insulin, oral antidiabetic medications do cross the placenta. 

Glyburide

Glyburide, which goes by the brand names Glynase, Diabeta, or Micronase, is a bit controversial. There are several studies supporting the efficacy and safety of glyburide for women with gestational diabetes, but ACOG does not recommend glyburide as a first-choice pharmacologic treatment because, in most studies, it does not yield equivalent outcomes to insulin or metformin. This is shown in one study that found an association between glyburide (compared with insulin) and elevated risk of NICU admission, neonatal hypoglycemia, respiratory distress, birth injury, and large for gestational age in women with gestational diabetes.

Metformin

The other option for an oral medication is metformin, which goes by the brand names Glumetza, Glucophage, Fortamet, or Riomet. This is generally considered safe during pregnancy, but there have been some questions about long-term effects on babies whose mothers took metformin. ACOG references numerous studies on metformin. Although ACOG acknowledges it may be a reasonable alternative, it is important to counsel women about the lack of superiority when compared with insulin, the placental transfer of the drug, and the absence of long-term data in exposed offspring. ACOG also notes that in the trials reviewed, 26-46% of women who took metformin alone eventually required insulin.

Discussing Medications with Your Care Provider

This was a brief overview of the medications to treat gestational diabetes. You will need to discuss any medicine’s details, risks, and benefits with your care provider. They likely will align with the guidance from ACOG that insulin is the preferred pharmacological treatment. Overall, ACOG repeatedly draws attention to the fact that oral antidiabetic medications are not approved by the FDA for the treatment of gestational diabetes, cross the placenta, and lack long-term neonatal safety data.

How Gestational Diabetes Changes Your Prenatal Care and Birth

In addition to treating gestational diabetes, this diagnosis can affect your prenatal care and birth in several ways.

Labeling Your Pregnancy High-Risk

High risk is a blanket term a care provider can apply for many reasons. The majority of care providers will likely consider gestational diabetes as high risk. This means they may be monitoring you more closely, and you may have more frequent appointments. In addition, if you are diagnosed with gestational diabetes, your care provider may recommend additional tests like a fetal non-stress test or a biophysical profile. A fetal non-stress test involves attaching one belt to the mother’s abdomen to measure fetal heart rate and another to measure contractions. Your care provider monitors movement, heart rate, and heart rate reactivity to movement for 20-30 minutes. A biophysical profile combines an ultrasound evaluation with a non-stress test to help determine fetal health.

Your Birth Options

A gestational diabetes diagnosis may limit your options of where you can have your birth. Most birth centers require you to have a normal, low-risk pregnancy. Some birth centers may be comfortable if you are managing gestational diabetes with diet and lifestyle and not taking medication. If you have gestational diabetes and are planning on birth at home, you will need to discuss your options with your midwife.

Labor Induction

Many care providers will recommend induction of labor for expecting mothers with gestational diabetes. The goal of induction is to prevent stillbirth and decrease the risks that come with your baby being at a higher weight, like shoulder dystocia, birth trauma, and cesarean birth.

There has been a lot of research on induction and gestational diabetes. In one study, researchers note that there is no definitive data on the timing and mode of delivery for pregnant women with gestational diabetes. If the patient has normal or near-normal glucose values, it is recommended that she should deliver at term. The general recommendation is that pregnancies complicated by gestational diabetes should not extend beyond term. Earlier delivery was associated with a reduction of macrosomia but not with a reduction of other neonatal complications. 

Another study looked at the delivery timing in women with gestational diabetes and broke down the risks and benefits of inducing labor. One of the problems is that this is often based on gestational age or ultrasound-estimated fetal weight. Estimated fetal weight is not very accurate. Some research even found mothers’ estimations were nearly as accurate as ultrasound estimates.

The researchers suggest that in the absence of clear evidence for routine guidelines, the decision on elective delivery should be made on an individual basis, taking into account a number of clinical factors, including gestational age, sonographic and clinical estimated fetal weight, Type of diabetes, degree of glycemic control, obstetrical history of the individual patient, how many children you have had and cervical status. Cervical status is relevant because induction tends to be more effective if your cervix has begun to dilate and efface. The potential benefits and risks of elective delivery should be discussed with the patient, and patient preference following such a discussion should also be included in the final decision on elective delivery.

The decision to recommend an induction includes many factors specific to your pregnancy. Inducing labor for a mother who has gestational diabetes has risks and benefits. These decisions can be challenging, and you will need to discuss your options, risks, and benefits with your care provider. See this episode for a breakdown of each method to induce labor, how it works, and the risks and benefits.

Babies with Hypoglycemia

Babies born to mothers with gestational diabetes are at a higher risk of being born with hypoglycemia, which is low blood sugar. As a result, many are supplemented with formula from the start to bring up their blood sugar levels. If you would like to avoid formula or decrease the odds that you will need to supplement with formula, you may consider collecting colostrum before your baby is born.

There are no clear guidelines on pumping or expressing colostrum during your pregnancy. Expecting mothers who choose to do this may start between 34-37 weeks. There has been concern that expressing colostrum can induce labor because stimulating your nipples produces oxytocin. Nipple stimulation is one method women use to try to naturally induce labor. One study has shown no increased risk for premature labor or delivery for women expressing colostrum. That study concludes that there is no harm in advising women with diabetes in pregnancy at low risk of complications to express breast milk from 36 weeks gestation. If you think collecting and storing colostrum is something you would like to do, please discuss it with your care provider. You can find more information on this topic from La Leche League.

Remember, this is Temporary

Pregnancy is hard enough for someone who is low-risk with no complications. Having gestational diabetes and being labeled high-risk can bring a new level of stress and anxiety. Gestational diabetes is one of the most common conditions during pregnancy. All you can do is do the best you can to employ diet and lifestyle changes to manage your blood sugar and make informed decisions about interventions like taking medications or inducing labor. Remember that gestational diabetes does go away after you have your baby. While it may not be comforting now, there is light at the end of the tunnel. Even if you are struggling with gestational diabetes now, it will all be worth it when holding your beautiful baby.

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